(1) Field of the Invention
The present invention relates to underwater guns and more specifically, to apparatus for preventing the entry of water into an underwater gun, for capturing a sabot, and for managing the propellant gases produced by firing the gun.
(2) Description of the Prior Art
Various underwater guns have been developed that utilize an explosive charge that must be kept dry and in the presence of air for proper detonation. Generally, such guns have utilized a single-use seal to prevent entry of water into either the gun or into a cartridge containing the explosive charge.
U.S. Pat. No. 3,585,934 discloses a disposable ammunition having a watertight barrel that is removably mounted into a carrier cylinder or block for firing. A head end cap assembly seals the breech end of the barrel and a closure cup seals the muzzle end of the barrel to provide a watertight enclosure. A propellant charge disposed in the barrel is ignited to propel a flechette from the barrel. The closure cup is destroyed as the flechette exits the barrel. Once the ammunition is fired, the barrel is removed and replaced with an unfired ammunition.
U.S. Pat. Nos. 4,651,454 and 4,742,775 each disclose a spear gun having a chamber in its breech for receiving an explosive power load. The power load has a closed end that is adapted to open when the propellant explodes. The closed end is sealed with a sealing compound to prevent the entry of water. Once the power load has been fired, the breech is opened and the spent power load is replaced with a new power load. A plurality of circumferential grooves in the breech end of the spear serve as pressure interrupters or dynamic seals to interfere with and inhibit the escape of the detonation gases within the barrel of the spear gun. Water is free to enter both the barrel and the breech of the spear gun.
It is also well known to provide projectiles in firearms with a sabot surrounding the projectile to enhance the projectile's muzzle velocity. Often this sabot is stripped away from the projectile during launch by the firearm thereby changing the projectile's flight characteristics.
The single use sealing systems of the prior art devices require replacement of the seal each time the underwater gun is fired. The seal is generally a part of a sealed unit such as the power load or ammunition discussed above. Therefore, replacement of the seal requires replacement of a larger structure. Consequently, such apparatus is limited in use to applications that allow access to this sealed unit. In addition, the time required to replace the sealed unit limits the speed at which multiple projectiles may be fired, and the prior art devices are either limited to single shot applications or require the use of multiple sealed units to permit rapid firing of multiple projectiles. Generally, the number of sealed units that can be supported is limited, thereby limiting the total number of projectiles that may be fired. Finally, prior art underwater guns do not control the propellant gasses once the projectile has been launched. The introduction of the propellant gasses into the surrounding water reduces the performance of the projectiles.